Discharge circuits are commonly used in battery charging, conditioning, calibration and other systems. In battery charging and conditioning systems, discharge circuits may be used to completely discharge a battery before beginning a charging cycle. For some battery types, such as nickel-cadmium batteries, they may have a “memory” of previous minimum charge levels such that shallow cycling can limit battery life. A discharge circuit is used in a battery charging system for such a battery to ensure such batteries last longer by deeply cycling the battery.
In battery calibration systems, a discharge circuit may be used to determine the characteristics of a battery. For some battery types, such as lithium-ion batteries, determining the characteristics of the battery under load conditions may assist in determining battery condition as it ages. Additionally, calibration systems produce information that allow predicting performance of the battery over its service life.
Discharge or calibration cycles may require extended periods of time without interruption to be effective. If the cycle is interrupted, the battery may have to be recharged before the cycle can begin anew, consuming even more time. Failure of the discharge circuit, power loss to the discharge circuit, or disconnecting of the battery from the circuit are all possible causes of interruption of the cycle.
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter suffix.